View of the cargo bay of Shuttle Columbia, showing the Spacelab Life Sciences SLS-1 module. SLS-1 was carried on Mission STS-40 of 5-14 June 1991. Its overall objective was to perform a wide variety of investigations into the pysiological conditioning of the crew to the microgravity environment in orbit. The crew entered the SLS-1 module through a tunnel, part of which is seen at bottom centre. The cargo doors of the Shuttle are kept open during flight as they contain radiators for temperature control on-board.